Method and apparatus for forming tube turns



Oct. 21,1958 c L. HITZ 2,856,981

1 METHOD AND APPARATUS FOR FORMING TUBE TURNS File d Aug. 19. 1955 IN V EN TOR.

United States PatetitO 75%,

METHOD AND APPARATUS FOR FORMING TUBE TURNS Gifford L. Hitz, Paola, Kans., assignor to The Fluor Corporation, Ltd., Los Angeles, Calif., a corporation of California Application August 19, 1955, Serial No. 529,379

11 Claims. (Cl. 153-48) This invention relates generally to forming of bends in metal tubes, and more specifically concerns novel methods and apparatus for progressively cold extruding metal tubesto produce bends therein, the metal tube wall being laterally expanded and deformed to physically displace the metal in a manner facilitating ease of bending and control of the tube wall thickness and shape during such bending.

It is a major object of the invention to provide means for cold extruding metal tubing in a manner productive toward the opposite side of the tube, the final step being to compressively deform said opposite side toward the tube axis so as to bend the tube away from that axis. The novel method essentially provides for stretching of the tube wall at the side thereof subsequently becoming the inside bend radius, followed by crowding of the metal at that side toward the opposite side of the tube, this process having the effect of adding to the metal available at said opposite side for ultimate stretching around the larger bend radius.

The novel tube bending apparatus provided comprises an elongated mandrel over which the metal tube is slidably receivable for guided travel, the mandrel having a projecting side portion for progressively expanding one side of the tube during travel over that portion, forced displacement of the tube being carried out by a novel pulling mechanism engageable with the tube. A pair of rotatable forming rolls are mounted at opposite sides of the mandrel beyond the projection in the direction of tube travel and in an axial plane passing through the projection, the rolls being relatively oifset in thatdirectionfor sequentially laterally deforming the expanded side of the tube and the opposite side thereof toward the tube axis, with the result that the tube is progressively shaped in the manner outlinedabove and in the desired bend form.

An important feature of the invention concerns placement of one of the forming rolls proximate to the projection formed at one side of the mandrel and inspaced relation to the portion thereof sloping back toward the mandrel axis The roll has a peripheral surface forming an annular concavity for tangential surface engagement with the expanded portion of the metal tube, the roll cooperating with the sloped portion of the projection to deform the expanded portion of the tube back toward the mandrel axis so that metal is displaced around the sides of the mandrel and toward the opposite side of the tube.; This arrangement facilitates bending of the tube around the end of the mandrel by the other roll which is similarly shaped, since metal is in etfect'supplied to that side of the tube which undergoes stretching during such final bending and is removed from that side of the tube which undergoes compression during bending. As a result, the bending process takes place under conditions favoring same, insofar'as working and stretching of the metal is concerned.

Other features of the invention include the: provision of suitable means for suspending the mandrel in position relative to the forming rolls, mechanism for engaging the tube and drawing it over the mandrel between the rolls, and a ratchet-type device connected to one of the rolls and actuated upon displacement of the tubing for rotating that roll at a surface speed equal to that of the side of the tubing engaged by the roll. Other features and ob-.

jects of the invention, as well as the details of an illustrative embodimentwill be more fully understood from the following detailed description of the drawings, in which:

Fig. 1 is a side elevation of the complete apparatus for producing bendsin the tube; I

Fig. 2 is a frontal elevationof the apparatus;

Fig. 3 is an enlarged sectionalview taken on line 3-3 of Fig. 2;

Fig. 4 is an enlarged fragmentary view ,of the lower end of the mandrel and portions of the rolls taken on line 4-4 of Fig. 3;

Fig. 5 is a fragmentary vie w taken. on line of Fig. 2 and illustrating details of the roll driving mechanism;

Fig. 6 is a section taken through the mandrel and tubing on line 6-6 of Fig. 4;

Fig. 7 is a similar section taken on line 7-7 of and Fig. 8 is a similar view taken on line .8-8 of Fig. 4.

Referring generally to Figs. 1 and 2, the completeap- Fig. 4;

paratus 10 includes horizontal table 11 mounted on vertical supports -12 and supporting parallel Vertically extending hydraulic cylinders 13. The latter are provided with inlet and outlet fittings 14 foradmitting and discharging hydraulic fluid to the cylinders acting to displace suitable pistons contained within the cylinders and parallel spaced draw bars 15 connected to the pistons and extendingupwardlythrough the table 11.

Referring to Figs. 3 and 4, an elongated generally cylindrical mandrel 16 is vertically suspended between are shown in Figs. 4 and 5, are positioned at oppositedraw bars 15 from a split nut17, the upper end of the mandrel being threaded to receive a smaller mandrel nut 18 hearing on the top surface of the split nut,17

and transferring mandrel loads thereto. The split nut is in turn carried by fixed support structure 19 and held thereto by transverse bolts 20 which are removable to permit disassembly of the split nut so that cross-piece 21 may be connected between the draw bars15 and to their upper end. The central bolt hole '22 in the split nut 17 is provided for reception of a centering pinrek ceivable. through the mandrel for centering it relative to the forming rolls to be described) I As better shown in Figs. 1 and 4, the lower end portion of the mandrel has a projection 23 at one side thereof, the projection being smoothly contoured in the direction of mandrel elongation, with upper and lower portions 24 and 25 sloping respectively concavely away from and toward the mandrel axis 26. The section on line 77 through the projection shows the mandrel to have an oval shape, at that point, and it will be understood that the degree of ovalness increases and decreases respectively at the sloped portions 24 and 25 of the projection.

Apair of forming rolls 27 and 28, portions of which 2,856,981 Patented Oct. 21, 195,8

sides of the mandrel beyond the projection in the direction of tube travel over the mandrel and in an axial plane 29 passing through the mandrel axis and through the projection, plane 29 being. indicated in Figs. 6 through 8. The rollsarerelatively offset in the direction of tube travel, with roll 27 being spaced laterally proximate to the-sloped portion of the mandrel projection and roll 28 being positioned proximate to the opposite side 30 of the mandrel curving toward the axis of the mandrel at the lower end portion thereof. Each of the forming rolls has a peripheral surface 31 forming an annular saddlelike concavity for tangential surface engagement with wall portions of the tube 32, which may be advanced along the mandrel in the manner to be described.

Referring to Figs. 1 and 4, that portion of the tube 32 passing over the lower end of the mandrel is illustrated as bending around forming: roll 27 between concave surface 31. thereof and the concave upper surface 33 of shoe 34. The latter is seated on table 11 beneath roll 27 in order to engage and guide the tubing after deformation thereof between the rolls 27 and 28, also as illustrated in Fig. 1. In addition, bending and advancement of the tubing around roll 27 is facilitated by adjustable clamp 35 mounted centrally upon concave surface 31 of roll 27 for engagement with the forward end 36 of the tubing. In those instances where experience shows that the tubing will bend sufficiently around roll 27 without guidance or clamping, either shoe 34 or clamp 35 may be dispensed with, the extruding action of roll 28 upon the tubingsuflicing to produce and maintain the desired bend.

Coming now to a description of the mechanism for advancing the tubing along the mandrel, Figs. 1 through 3 illustrate a split drive sleeve 37 encircling the upper end of the mandrel beneath cross-piece 21 and confined in position by split sleeve 38 threaded into the under side of the cross-piece. The drive sleeve has an inclined lower end 39 for engagement with the correspondingly inclined rearward end 40 of the tube, as shown in Fig. 3, the purpose of the tubing inclination being the production of a true or square tube end after completion of the bend. As is apparent, sleeve 38 is dimensioned to confine the drive sleeve between the mandrel and sleeve 38 and in engagement with the rearward end of the tubing so that when cross-piece 21 is pulled downwardly by draw bars 15, the drive sleeve will force the tubing along the mandrel. To facilitate advancement of the tubing between roll 27 and the inwardly sloping portion 25 of projection 23 on the mandrel, roll 27 is driven in rotation by a ratchet mechanism 41 illustrated in Fig. 5. The latter mechanism may typically include a toothed wheel 42 keyed to the shaft 43 driving roll 27, and a rack assembly 44 mounted on one draw bar 15 and having cogs 144 engaging corresponding cogs on wheel 42. The rack assembly is shown in Fig. 5 to be laterally displaceable out of engagement with the toothed wheel so that the cogs may disengage and slip relatively over one another during the upstroke of the draw bars 15. Compression springs 45 at opposite ends of the rack assembly are mounted to urge the assembly laterally toward the toothed wheel 42 for cog engagement and wheel rotation as during downstroke of the draw bar 15, while allowing lateral displacement of the assembly away from the toothed wheel, for the purpose stated above.

A complete operating cycle of the mechanism includes cutting the tubing 32 to length, followed by special lubrication of its inner and outer surfaces. For this purpose, the tubing should be treated with a dry type phosphate lubricant such as Zinc phosphate sold under the tradename Oakite Cryscote HC. A grease type lubricant applied to the external surfaces of the mandrel 16 and surfaces 31 of the rolls 27 and 28 serves in conjunction with the phosphate coating on the tubing to effectively eliminate galling and to promote ease of tube bending during extension.

V and then the opposite side thereof to continuously bend The pipe is then lowered onto the mandrel 16, crosspiece 21 placed over the end of the mandrel and con nected to the upper ends of :the draw bars 15 to mount the mandrel in vertical position against displacement, and nut 18 is threaded onto the upper end of the mandrel and brought into engagement with split nut 17, the latter having been previously connected by bolts 20. To complete preparation for advancing the tube along the mandrel, the split drive sleeve 37 is assembled between cross-piece 21 and the rearward end of the tubing, followed by threaded connection of the confining split sleeve 38 into the crosspiece, as better shown in Fig. 3.

With the forward end of the tubing resting against the sloped upper portion 24 of the projection 23 on the mandrel, hydraulic cylinders 13 are actuated to downwardly displace the tubing over the projection 23, movement of the draw bars 15 transmitting rotation to roll 27 so that as the one side of the tubing is expanded over the projection 23, it is subsequently engaged by surface 31 of roll 27 traveling at the same speed and deformed back toward the axis 26 of the mandrel, as shown in Fig. 4.

Such deformation of the tubing back toward axis 26 as effected by roll 27 causes displacement of tube metal toward the opposite side of the tubing and also in directions normal to plane 29. In other words, tube metal is forced toward the opposite side of the tube which subsequently undergoes stretching during bending around roll 27, as produced by idling roll 28. To accommodate such metal displacement, surfaces 31 of both of the forming rolls on opposite sides of plane 29 are spaced apart sufficiently as shown in Fig. 8 to form widened gaps 46 between the mandrel and the surfaces 31 and into which tube metal may be expanded. Since Fig. 8 shows the condition of the tube wall after bending around roll 27 has begun, the gaps 46 are no longer filled with tube metal, the latter having been stretched laterally toward the outer or opposite side of the tubing at the larger bend radius during such bending. The result of deformation of the metal produced by projection 23 and rolls 27 and 28 consists in maintenance of substantially uniform wall thickness of the tubing after the bend has been developed so that tube strength is not impaired, and the facilitation of overall extruding action.

As the hydraulic cylinders 13 may have only a short stroke, they may be re-cycled several times until the tube bend is advanced completely around roll 27. After initial starting of the bend, the clamp 35 may be fastened to the forward end of the tube passing between roll 27 and shoe 34. Mandrel 16 is shown in Fig. 4 to terminate approximately between rolls 27 and 28; however, it may be brought around for any desired distance in the path followed by the tubing subsequent to bending thereof around roll 27 I claim:

1. Apparatus for progressively bending a metal tube,

comprising an axially elongated mandrel over which said tube is receivable for guided travel therealong, said mandrel having at one side portion thereof a projection sloping away from the mandrel axis in the direction of tube travel for progressively expanding one side of said tube during said travel, movable means engageable with said tube for displacing it along said mandrel in said direction, and a pair of forms extending in the travel path of both the expanded side of the tubing and the opposite side thereof for engagement therewith in said direction and in an axial plane passing through said projection, said forms being relatively offset in said direction for sequentially laterally deforming toward said axis the expanded side of said tube the tube away from said axis.

2. Apparatus for progressively bending a straight metal tube, comprising an axially elongated mandrel over which said tube is slidably receivable for guided travel therealong, said mandrel having at one side portion thereof a projection parts of which slope away from and toward the .5 mandrel axis in the direction of tube travel for progressively expanding one side of the tube during said travel, movable means engageable with tube for displacing it axially relative to said mandrel, and a pair of forms extending in the travel path of both the expanded side of the tubing and the opposite side thereof for engagement therewith in said direction and in an axial plane passing through said projection, one of said forms being positioned proximate to the part of said projection sloping toward the mandrel axis and the other of said forms being relatively offset from the first form in said direction for sequentially laterally deforming toward said axis the expanded side of said tube and then the opposite side thereof to continuously bend the tube away from said axis and relatively around said one form.

3. Apparatus for progressively bending a straight metal tube, comprising an axially elongated mandrel over which said tube is slidably receivable for guided travel therealong, said mandrel having at one side portion thereof a transversely oval-shaped projection parts of which slope away from and toward the mandrel axis in the direction of tube travel for progressively expanding one side of the tube during said travel, movable means engageable with said tube for displacing it axially relative to said mandrel, and a pair of rotatable forming rolls extending in the travel path of both the expanded side of the tubing and the opposite side thereof for engagement therewith, one of said rolls being positioned proximate to the part of said projection sloping toward the mandrel axis and the other of said rolls being relatively offset from the first roll in said direction for sequentially laterally deforming toward said axis the expanded side of said tube and then the opposite side thereof to continuously bend the tube away from said axis and relatively around said one roll.

4. Apparatus for progressively bending a straight metal tube, comprising an axially elongated mandrel over which said tube is slidably receivable for guided travel therealong, said mandrel having at one side portion thereof a projection parts of which slope away from and toward the mandrel axis in the direction of tube travel for progressively expanding one side of the tube during said travel, said mandrel having beyond said projection in said direction an opposite side portion sloping toward said axis in said direction, movable means engageable with said tube for displacing it axially relative to said mandrel, and a pair of rotatable forming rolls extending in the travel path of both the expanded side of the tubing and the opposite side thereof for engagement therewith, said rolls being positioned respectively proximate to the part of said projection sloping toward the mandrel and proximate to said opposite side portion of the mandrel for sequentially laterally deforming toward said axis the expanded side of said tube and then the opposite side thereof to continuously bend the tube away from said axis.

5. Apparatus for progressively bending a straight metal tube, comprising an axially elongated mandrel over which said tube is slidably receivable for guided travel therealong, said mandrel having at one side portion there- 6 Y of a transversely oval-shaped projection parts of which slope away from and toward the mandrel axis in the direction of tube travel for progressively expanding one side'of the table during said travel, said mandrel having beyond said projection in said direction an opposite Side portion sloping toward said axis in said direction, movable means engageable with one end of said tube for displacing it along said mandrel in said direction, and a pair of rotatable forming rolls extending in the travel path of both the expanded side of the tubing and the opposite side thereof for engagement therewith, one of said rolls being positioned proximate to the part of said projection sloping toward the mandrel axis and the other of said rolls being positioned proximate to said opposite side portion of the mandrel for sequentially laterally deforming toward said axis first the expanded side of said tube and then the opposite side thereof to continuously bend the tube away from said axis and relatively around said one roll.

6. The invention as defined in claim 5 in which each of said rolls has a peripheral surface forming an annular concavity for tangential surface engagement with said tube.

7. The invention as defined in claim 6 in which portions of said surface are symmetrically located relative to an axial plane through said projection and to form gaps between said mandrel and said surface into which the tube wall is deformable.

8. The invention as defined in claim 7 in which said part of the projection sloping toward the mandrel axis is spaced from the peripheral surface of said one roll and curved in substantial conformity therewith to form therebetween a space into which the expanded side of the tube is deformable toward said axis.

9. The invention as defined in claim 6 in which said means comprises a sleeve slidably mounted on said mandrel behind said tube in the direction of travel thereof.

10. The invention as defined in claim 9 including hydraulically actuated mechanism operatively connected with said sleeve for displacing it axially relative to said mandrel.

11. The invention as defined in claim 10 including a connection between said mechanism and said one roll for transmitting thereto rotation productive of peripheral surface speeds substantially equal to the speed of travel of said tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,353,714 Bohling Sept. 21, 1920 1,370,074 Vasselli Mar. 1, 1921 1,908,373 Loepsinger May 9, 1933 2,181,384 Taylor Nov. 28, 1939 2,242,332 Taylor May 20, 1941 2,318,113 Taylor May 4, 1943 FOREIGN PATENTS 329,209 Germany Nov. 15, 1920 607,325 Germany Dec. 21, 1934 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,856,981 October 21, 1958 Gifford L a Hitz It is herebfi certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

, and column 5, lines '7 and 8, strike out Column 4, lines 65 and 66 Xial plane passing through said projection",

"in said direction and in an a each occurrence.

Signed and sealed this 10th day of February 1959a (SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Commissioner of Patents Attesting Ofiicer 

